Roll Polymer to 1.3.1

third_party/polymer/v1_0/components-chromium/iron-selector/iron-selection-extracted.js

 /**
    * @param {!Function} selectCallback
    * @constructor
    */
   Polymer.IronSelection = function(selectCallback) {
     this.selection = [];
     this.selectCallback = selectCallback;
   };
 
   Polymer.IronSelection.prototype = {
@@ skipping 37 matching lines @@
 
     /**
      * Sets the selection state for a given item to either selected or deselected.
      *
      * @method setItemSelected
      * @param {*} item The item to select.
      * @param {boolean} isSelected True for selected, false for deselected.
      */
     setItemSelected: function(item, isSelected) {
       if (item != null) {
-        if (isSelected) {
-          this.selection.push(item);
-        } else {
-          var i = this.selection.indexOf(item);
-          if (i >= 0) {
-            this.selection.splice(i, 1);
+        if (isSelected !== this.isSelected(item)) {
+          // proceed to update selection only if requested state differs from current
+          if (isSelected) {
+            this.selection.push(item);
+          } else {
+            var i = this.selection.indexOf(item);
+            if (i >= 0) {
+              this.selection.splice(i, 1);
+            }
           }
-        }
-        if (this.selectCallback) {
-          this.selectCallback(item, isSelected);
+          if (this.selectCallback) {
+            this.selectCallback(item, isSelected);
+          }
         }
       }
     },
 
     /**
      * Sets the selection state for a given item. If the `multi` property
      * is true, then the selected state of `item` will be toggled; otherwise
      * the `item` will be selected.
      *
      * @method select
@@ skipping 12 matching lines @@
      * Toggles the selection state for `item`.
      *
      * @method toggle
      * @param {*} item The item to toggle.
      */
     toggle: function(item) {
       this.setItemSelected(item, !this.isSelected(item));
     }
 
   };